Many authors take "Zermelo-Fraenkel" (ZF) to refer to these axioms without the axiom of choice, indicating the inclusion of choice by writing "ZFC".
The Axiom of Choice is independent of (i.e. neither provable nor disprovable from) the Zermelo-Fraenkel axioms. Sometimes alternate axioms are added to ZF, for example the Axiom of Determinacy, which is incompatible with the Axiom of Choice.